Friday, September 26, 2014

The study shows that the
familiar anatomical features of birds – such as feathers, wings and
wishbones – all first evolved piecemeal in their dinosaur ancestors over
tens of millions of years. However, once a fully functioning bird body
shape was complete, an evolutionary explosion began, causing a rapid
increase in the rate at which birds evolved. This led eventually to the
thousands of avian species that we know today.

Researchers
examined the evolutionary links between ancient birds and their closest
dinosaur relatives, by analyzing the anatomical make-up of more than 850
body features in 150 extinct species, and used statistical techniques
to analyze their findings and assemble a detailed family tree.

Credit: Steve Brusatte

The most
comprehensive family tree of meat-eating dinosaurs ever created is
enabling scientists to discover key details of how birds evolved from
them.

The study, published in the journal Current Biology, shows
that the familiar anatomical features of birds -- such as feathers,
wings and wishbones -- all first evolved piecemeal in their dinosaur
ancestors over tens of millions of years.

However, once a fully functioning bird body shape was complete, an
evolutionary explosion began, causing a rapid increase in the rate at
which birds evolved. This led eventually to the thousands of avian
species that we know today.

A team of researchers, led by the University of Edinburgh (UK) and
including Swarthmore College Associate Professor of Statistics Steve C.
Wang, examined the evolutionary links between ancient birds and their
closest dinosaur relatives. They did this by analyzing the anatomical
make-up of more than 850 body features in 150 extinct species and used
statistical techniques to analyze their findings and assemble a detailed
family tree.

Based on their findings from fossil records, researchers say the
emergence of birds some 150 million years ago was a gradual process, as
some dinosaurs became more bird-like over time. This makes it very
difficult to draw a dividing line on the family tree between dinosaurs
and birds.

Findings from the study support a controversial theory proposed in
the 1940s that the emergence of new body shapes in groups of species
could result in a surge in their evolution.

"The evolution of birds from their dinosaur ancestors was a landmark
in the history of life," says Wang. "This process was so gradual that if
you traveled back in time to the Jurassic, you'd find that the earliest
birds looked indistinguishable from many other dinosaurs."

Wang invented a novel statistical method that was able to take
advantage of new kinds of data from the fossil record, which reached the
conclusion that early birds had a high rate of evolution. He adds that
"birds as we know them evolved over millions of years, accumulating
small shifts in shape and function of the skeleton. But once all these
pieces were in place to form the archetypal bird skeleton, birds then
evolved rapidly, eventually leading to the great diversity of species we
know today."

"There was no moment in time when a dinosaur became a bird, and there
is no single missing link between them, " says Steve Brusatte of the
University of Edinburgh's School of GeoSciences, who led the study.
"What we think of as the classic bird skeleton was pieced together
gradually over tens of millions of years. Once it came together fully,
it unlocked great evolutionary potential that allowed birds to evolve at
a super-charged rate."

The work was supported by the European Commission, National Science
Foundation, the University of Edinburgh, Swarthmore College's Research
Fund, Swarthmore College's James Michener Faculty Fellowship, Columbia
University, and the American Museum of Natural History.

Story Source:
The above story is based on materials provided by Swarthmore College. Note: Materials may be edited for content and length.

Increased snowfall will
not prevent the continued melting of glaciers in the northern Antarctic
Peninsula, according to new research. Scientists have discovered that
small glaciers that end on land around the Antarctic Peninsula are
highly vulnerable to slight changes in air temperature and may be at
risk of disappearing within 200 years.

Increased
snowfall will not prevent the continued melting of glaciers in the
northern Antarctic Peninsula, according to new research published in the
journal Nature Climate Change.

An international team of researchers, led by Dr Bethan Davies, from
Royal Holloway, University of London, has discovered that small glaciers
that end on land around the Antarctic Peninsula are highly vulnerable
to slight changes in air temperature and may be at risk of disappearing
within 200 years.

Temperatures are currently rising rapidly in the Antarctic Peninsula.
Because warmer air holds more moisture, the amount of snowfall has also
increased. Some researchers have suggested that this may offset the
melting of the glaciers, however this study found that just a small rise
in air temperature increased melting so much that even large amounts of
extra snowfall could not prevent glacier recession.

"These small glaciers around the edge of the Antarctic Peninsula are
likely to contribute most to rising sea levels over the coming decades,
because they can respond quickly to climate change," said Dr Davies,
from the Department of Geography at Royal Holloway. "This study is the
first to show how glaciers in this vulnerable region are likely to
respond to climate change in future. Our findings demonstrate that the
melting will increase greatly even with a slight rise in temperature,
offsetting any benefits from increased snowfall."

The researchers carried out extensive fieldwork on James Ross Island,
northern Antarctic Peninsula, to map and analyse the changes to a
glacier, which is currently 4km long, over the past 10,000 years. They
used a combination of glacier and climate modelling, glacial geology and
ice-core data.Dr Davies added: "Geological evidence from previous studies suggests
that the glacier grew by 10km within the last 5,000 years, before
shrinking back to its current position. It was argued that this occurred
during a warmer but wetter period, suggesting that increased
precipitation in the future would offset the melting of the glaciers.
However, our study shows that this growth occurred during the colder
'Little Ice Age', reaching its largest size just 300 years ago."

Researcher Dr Nicholas Golledge, from Victoria University of
Wellington, in New Zealand, said: "This glacier, though small, is
typical of many of the small glaciers that end on land around the
Antarctic Peninsula. This research is important, because it helps reduce
some of the uncertainties about how these glaciers will react to
changing temperature and precipitation over the next two centuries."

Professor Neil Glasser, from Aberystwyth University, added: "We found
that this glacier remained roughly the same size for thousands of years
until it started to grow again 1,500 years ago. However, it is now
melting faster than anything seen before, and over the next 200 years
will become far smaller than at any point over the last 10,000 years.
This unprecedented glacier recession, in response to climate change,
will result in significant contributions to sea level rise from this and
similar Antarctic Peninsula mountain glaciers and ice caps."

Saturday, September 6, 2014

Researchers in Antarctica on a mission to locate penguin colonies
found two groups of seabirds, thanks to a little help from satellites,
helicopters, and the detection of more “primitive” evidence: penguin
poop.

Our favorite tuxedo-clad Emperor penguin
is native to Antarctica, but harsh winter conditions and the remoteness
of some colonies can make it difficult for biologists to gain a
comprehensive population assessment of this “hiding” bird. The first
breeding penguin colony was discovered in Antarctica in 1902, and in
1999 thousands of birds were sighted near the Mertz glacier in Antarctica, but for the last century, suspected colonies of Emperor Penguins in the area had yet to be confirmed.

In this recently published PLOS ONE study,
the authors used both survey- and satellite-based methods to locate the
presence of Emperor penguin colonies on the Mertz glacier, where a
previous sighting of thousands of birds had occurred 15 years ago, but a
drastic habitat change—the glacier’s “tongue” broke off in February
2010—may have disrupted.

Aerial surveys captured two new potential breeding grounds for
colonies, the Eastern and Western (~7,400 breeding pairs total).
Satellite images from a thousand feet in the sky helped the authors
detect the Eastern colony by the presence of fecal marks—or in bird
specialist speak, “guano”—in the snow.

The red arrow in the image above points out the lovely brown streak
of guano strewn across the ice shelf, which indicates the Eastern
colony’s previous breeding ground. The authors used this streak as an
indication that the Eastern colony was likely close by. Below the
guano-streaked, snow-packed shelf, the presence of the Eastern colony
was confirmed by researchers trekking across treacherous terrain to
visually confirm the presence of the birds.

Unlike the Eastern colony, who mobilized to a fresh home
post-breeding, the Western colony seemingly didn’t mind remaining in
their breeding muck. This colony was discovered not by satellite but by
chance during helicopter flight operations in Antarctica. Although the
authors had difficulties finding the Western colony by aerial footage,
as pictured in the below image, these social gatherers appeared to
differ from the Eastern colony in that they inhabited a large flat
surface, and the colony appeared to be much larger.

In the cases of both colonies, aerial surveys appeared to be very
effective for locating them. So, until humans evolve warmer winter
coats, scientists conducting surveys by foot are still limited by frigid
conditions and isolated locations in future South Pole endeavors. To
obtain a more accurate picture of total penguin counts, the authors
suggest taking multiple aerial images during the breeding season and
conducting several-year surveys to confirm numbers in suspected
Antarctic penguin colonies. But for now, the game of Hide and Go Poop
will continue.

Wednesday, September 3, 2014

The gravity of the
world's current extinction rate becomes clearer upon knowing what it was
before people came along. A new estimate finds that species die off as
much as 1,000 times more frequently nowadays than they used to. That's
10 times worse than the old estimate of 100 times.

Vintage engraving
of the Dodo (Raphus cucullatus), a flightless bird endemic to the Indian
Ocean island of Mauritius. The dodo has been extinct since the
mid-to-late 17th century.

Credit: iStockphoto

The gravity
of the world's current extinction rate becomes clearer upon knowing
what it was before people came along. A new estimate finds that species
die off as much as 1,000 times more frequently nowadays than they used
to. That's 10 times worse than the old estimate of 100 times.

It's hard to comprehend how bad the current rate of species
extinction around the world has become without knowing what it was
before people came along. The newest estimate is that the pre-human rate
was 10 times lower than scientists had thought, which means that the
current level is 10 times worse.

Extinctions are about 1,000 times more frequent now than in the 60
million years before people came along. The explanation from lead author
Jurriaan de Vos, a Brown University postdoctoral researcher, senior
author Stuart Pimm, a Duke University professor, and their team appears
online in the journal Conservation Biology. "This reinforces the urgency to conserve what is left and to try to
reduce our impacts," said de Vos, who began the work while at the
University of Zurich. "It was very, very different before humans entered
the scene."

In absolute, albeit rough, terms the paper calculates a "normal
background rate" of extinction of 0.1 extinctions per million species
per year. That revises the figure of 1 extinction per million species
per year that Pimm estimated in prior work in the 1990s. By contrast,
the current extinction rate is more on the order of 100 extinctions per
million species per year.

Orders of magnitude, rather than precise numbers are about the best
any method can do for a global extinction rate, de Vos said. "That's
just being honest about the uncertainty there is in these type of
analyses."

From fossils to genetics

The new estimate improves markedly on prior ones mostly because it
goes beyond the fossil record. Fossils are helpful sources of
information, but their shortcomings include disproportionate
representation of hard-bodied sea animals and the problem that they
often only allow identification of the animal or plant's genus, but not
its exact species.

What the fossils do show clearly is that apart from a few cataclysms
over geological periods -- such as the one that eliminated the dinosaurs
-- biodiversity has slowly increased.

The new study next examined evidence from the evolutionary family
trees -- phylogenies -- of numerous plant and animal species.
Phylogenies, constructed by studying DNA, trace how groups of species
have changed over time, adding new genetic lineages and losing
unsuccessful ones. They provide rich details of how species have
diversified over time.

"The diversification rate is the speciation rate minus the extinction
rate," said co-author Lucas Joppa, a scientist at Microsoft Research in
Redmond, Wash. "The total number of species on earth has not been
declining in recent geological history. It is either constant or
increasing. Therefore, the average rate at which groups grew in their
numbers of species must have been similar to or higher than the rate at
which other groups lost species through extinction."

The work compiled scores of studies of molecular phylogenies on how fast species diversified.For a third approach, de Vos noted that the exponential climb of
species diversity should take a steeper upward turn in the current era
because the newest species haven't gone extinct yet."It's rather like your bank account on the day you get paid," he
said. "It gets a burst of funds -- akin to new species -- that will
quickly become extinct as you pay your bills."

By comparing that rise of the number of species from the as-yet
unchecked speciation rate with the historical trend (it was
"log-linear") evident in the phylogenies, he could therefore create a
predictive model of what the counteracting historical extinction rate
must have been.

The researchers honed their models by testing them with simulated
data for which they knew an actual extinction rate. The final models
yielded accurate results. They tested the models to see how they
performed when certain key assumptions were wrong and on average the
models remained correct (in the aggregate, if not always for every
species group).

All three data approaches together yielded a normal background
extinction rate squarely in the order of 0.1 extinctions per million
species per year.

A human role

There is little doubt among the scientists that humans are not merely
witnesses to the current elevated extinction rate. This paper follows a
recent one in Science, authored by Pimm, Joppa, and other
colleagues, that tracks where species are threatened or confined to
small ranges around the globe. In most cases, the main cause of
extinctions is human population growth and per capita consumption,
although the paper also notes how humans have been able to promote
conservation.

The new study, Pimm said, emphasizes that the current extinction rate is a more severe crisis than previously understood. "We've known for 20 years that current rates of species extinctions
are exceptionally high," said Pimm, president of the conservation
nonprofit organization SavingSpecies. "This new study comes up with a
better estimate of the normal background rate -- how fast species would
go extinct were it not for human actions. It's lower than we thought,
meaning that the current extinction crisis is much worse by comparison."

Other authors on the paper are John Gittleman and Patrick Stephens of the University of Georgia.

Story Source:
The above story is based on materials provided by Brown University. Note: Materials may be edited for content and length.